lib/ringbuffer/ring_buffer_mmap.c

   1 /*
   2  * ring_buffer_mmap.c
   3  *
   4  * Copyright (C) 2002-2005 - Tom Zanussi <zanussi@us.ibm.com>, IBM Corp
   5  * Copyright (C) 1999-2005 - Karim Yaghmour <karim@opersys.com>
   6  * Copyright (C) 2008-2012 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; only version 2 of the License.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License along
  18  * with this program; if not, write to the Free Software Foundation, Inc.,
  19  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Re-using code from kernel/relay.c, hence the GPLv2 license for this
  22  * file.
  23  */
  24
  25 #include <linux/module.h>
  26 #include <linux/mm.h>
  27
  28 #include "../../wrapper/ringbuffer/backend.h"
  29 #include "../../wrapper/ringbuffer/frontend.h"
  30 #include "../../wrapper/ringbuffer/vfs.h"
  31
  32 /*
  33  * fault() vm_op implementation for ring buffer file mapping.
  34  */
  35 static int lib_ring_buffer_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
  36 {
  37         struct lib_ring_buffer *buf = vma->vm_private_data;
  38         struct channel *chan = buf->backend.chan;
  39         const struct lib_ring_buffer_config *config = &chan->backend.config;
  40         pgoff_t pgoff = vmf->pgoff;
  41         struct page **page;
  42         void **virt;
  43         unsigned long offset, sb_bindex;
  44
  45         /*
  46          * Verify that faults are only done on the range of pages owned by the
  47          * reader.
  48          */
  49         offset = pgoff << PAGE_SHIFT;
  50         sb_bindex = subbuffer_id_get_index(config, buf->backend.buf_rsb.id);
  51         if (!(offset >= buf->backend.array[sb_bindex]->mmap_offset
  52               && offset < buf->backend.array[sb_bindex]->mmap_offset +
  53                           buf->backend.chan->backend.subbuf_size))
  54                 return VM_FAULT_SIGBUS;
  55         /*
  56          * ring_buffer_read_get_page() gets the page in the current reader's
  57          * pages.
  58          */
  59         page = lib_ring_buffer_read_get_page(&buf->backend, offset, &virt);
  60         if (!*page)
  61                 return VM_FAULT_SIGBUS;
  62         get_page(*page);
  63         vmf->page = *page;
  64
  65         return 0;
  66 }
  67
  68 /*
  69  * vm_ops for ring buffer file mappings.
  70  */
  71 static const struct vm_operations_struct lib_ring_buffer_mmap_ops = {
  72         .fault = lib_ring_buffer_fault,
  73 };
  74
  75 /**
  76  *      lib_ring_buffer_mmap_buf: - mmap channel buffer to process address space
  77  *      @buf: ring buffer to map
  78  *      @vma: vm_area_struct describing memory to be mapped
  79  *
  80  *      Returns 0 if ok, negative on error
  81  *
  82  *      Caller should already have grabbed mmap_sem.
  83  */
  84 static int lib_ring_buffer_mmap_buf(struct lib_ring_buffer *buf,
  85                                     struct vm_area_struct *vma)
  86 {
  87         unsigned long length = vma->vm_end - vma->vm_start;
  88         struct channel *chan = buf->backend.chan;
  89         const struct lib_ring_buffer_config *config = &chan->backend.config;
  90         unsigned long mmap_buf_len;
  91
  92         if (config->output != RING_BUFFER_MMAP)
  93                 return -EINVAL;
  94
  95         mmap_buf_len = chan->backend.buf_size;
  96         if (chan->backend.extra_reader_sb)
  97                 mmap_buf_len += chan->backend.subbuf_size;
  98
  99         if (length != mmap_buf_len)
 100                 return -EINVAL;
 101
 102         vma->vm_ops = &lib_ring_buffer_mmap_ops;
 103         vma->vm_flags |= VM_DONTEXPAND;
 104         vma->vm_private_data = buf;
 105
 106         return 0;
 107 }
 108
 109 int lib_ring_buffer_mmap(struct file *filp, struct vm_area_struct *vma,
 110                 struct lib_ring_buffer *buf)
 111 {
 112         return lib_ring_buffer_mmap_buf(buf, vma);
 113 }
 114 EXPORT_SYMBOL_GPL(lib_ring_buffer_mmap);
 115
 116 /**
 117  *      vfs_lib_ring_buffer_mmap - mmap file op
 118  *      @filp: the file
 119  *      @vma: the vma describing what to map
 120  *
 121  *      Calls upon lib_ring_buffer_mmap_buf() to map the file into user space.
 122  */
 123 int vfs_lib_ring_buffer_mmap(struct file *filp, struct vm_area_struct *vma)
 124 {
 125         struct lib_ring_buffer *buf = filp->private_data;
 126         return lib_ring_buffer_mmap(filp, vma, buf);
 127 }
 128 EXPORT_SYMBOL_GPL(vfs_lib_ring_buffer_mmap);